Generally, a bicycle is classified into three: a general bicycle as transport means, a mountain bicycle exclusively used for a mountain exercise and cycles used for a sporting event. Basically, the above all bicycles include front and rear wheels before and after a bicycle frame and a pair of pedals as a power supply source between two wheels. The driving force for bicycle is obtained through pedaling and then the force is transmitted to the rear wheel via a driving sprocket, a chain and a driven sprocket in sequence. However, most of bicycles can travel forward only when pedaling forward. That is, the bicycle cannot travel forward when pedaling rearward. This kind of one-directional bicycle causes easily fatigue in rider's leg and uneven development in a leg muscle when the rider bicycles for many hours.
Thus, in order to solve the problems, many inventors have made an effort in the development of a bi-directional pedaling apparatus which can be applied to a conventional one-directional bicycle. The bi-directional pedaling apparatus developed until now, which allows the bicycle to travel forward both when pedaling forward and rearward, may be classified into three roughly according to methods adopted therefor. That is, there are methods using an auxiliary gear, a bevel gear and a planetary gear. Here, the bi-directional pedaling apparatus is referred to a device in which a bicycle can travel forward at all times when pedaling the bicycle forward or rearward, and an idling is also allowed by selectively controlling a lever if required when pedaling the bicycle rearward, like a conventional bicycle.
As a representative invention related to the bi-directional pedaling apparatus. Manrzoursos et al. (EPO Publication No. 0.369,925) discloses a bi-directional pedaling apparatus adopting the auxiliary gear, Foster (U.S. Pat. No. 5,435,583) discloses a bi-directional pedaling apparatus adopting the bevel gear and a clutch. and the present applicant (Application No. PCT/KR 96/00236) discloses a bi-directional pedaling apparatus adopting the planetary gear.
The above inventions have a mid gear (auxiliary gear, bevel gear and planetary gear) in common in order to change the direction of power, however, also have difference in a method for changing the power direction, distribution degree of load applied to each part during the change of power, preciseness of parts and compatibility with a conventional bicycle. However, all of the inventions are developed to be attachable to a pedal shaft, not to a shaft of the rear wheel.
Particularly, the bi-directional pedaling apparatus (Application No. PCT/KR 96/00236) invented by the present applicant has many advantages in the aspects of preciseness of parts, smoothness in the change of power, compatibility to be directly attachable to a pedal shaft of the conventional bicycle. However, the shapes of the driving sprocket and a crank portion are different from those of the conventional bicycle, so that these parts should be changed by new ones when attaching the apparatus to the conventional bicycle.
Also, since the bi-directional pedaling apparatus invented by the present applicant is attached to the outside of the pedal shaft like the above-described apparatuses, the attached apparatus is protruded toward the outside of the bicycle frame. The protruded apparatus may obstruct the pedaling by a rider. In addition, it is difficult to attach the bi-directional pedaling apparatus protruded toward the outside of the bicycle frame to a newly developed bicycle which can be folded for portable transportation.
Thus, the above problems have raised requirements in development of a new bi-directional pedaling apparatus which can be attached to a shaft of the rear wheel.
On the other hand, in order to reduce fatigue in legs during pedaling and effectively utilize energy applied to the pedals, a pedaling rhythm and pedaling force applied to the pedals should be constant. A transmission for a bicycle is developed for satisfying the above conditions, which controls a gear ratio between a driving sprocket and a driven sprocket, thereby properly applying the pedaling force according to a driving resistance to the driving of bicycle.
As for the transmission, there are an external type and an internal type. The external transmission directly changes the gear ratio while applying a chain on a plurality of sprockets having different diameters in sequence which are installed at a pedal shaft and a hub shaft, and the internal transmission changes the gear ratio by installing planetary gears in a body of the rear hub. The internal transmission can be much miniaturized compared with the external transmission and protected from external impact while blocking the influx of dust or foreign substance since the internal transmission is installed in the hub shell. Due to these advantages, the internal transmission is widely adopted for the general bicycle. Here, Japanese Laid-open Patent Publication No. Heisei 5-65094 (dated Mar. 3, 1993) may be referred as an example of the inventions related to the internal transmission.
There are further inventions related to the internal transmission installed in the rear hub, which are for increasing efficiency of the transmission itself or controlling the gear ratio. However, an internal transmission including a bi-directional pedaling device for changing the power direction is unknown.
As described above, most of bi-directional pedaling devices have been installed to the pedal shaft, not to a hub shaft of the rear wheel. Also, most inventions related to the hub shaft is limited to only the transmission and it is difficult to find a multipurpose bicycle including both the transmission and the bi-directional pedaling device.
Thus, requirements for a multipurpose apparatus of a bicycle in which the bi-directional pedaling device for balanced development of muscle in human legs and the transmission for effectively utilizing energy applied to the pedal, and simultaneously a bicycle which has high safety and convenience in handling by installing all parts therein have been increased.